Thank you for the feedback and your interest in Freescale products. I think your assumptions are right, I will try to explain each case briefly to give you a better understanding.

1) Kinetis SDK - Enabled, Processor Expert Disabled: In this case the KSDK drivers are used, you can see the list of modules and drivers in the Kinetis SDK v.x.x API Reference Manual that is present in the doc folder in the KSDK installation path. This options uses just the KSDK drivers and there is no graphic configuration for the peripherals.

2) KSDK Enabled, PE Enabled: In this case the KSDK drivers are also used but the peripheral configurations are done by the graphic interface of Processor expert. Then you can add components and configure them using the graphic solutions. When writing your application you need to refer to the KSDK drivers and use them. While you do not add any OS Component to your project it will be a Bare Metal project but you always have the option to add a OS to your project.

3) KSDK Enabled, PE Enabled, osa.OS=MQX_KSDK: This is like you mentioned the same as the Case 2 but with a OS included, in this case MQX.